The present invention relates to a method of manufacturing a dense silicon carbide ceramic.
A known method of manufacturing dense silicon carbide ceramics is described in the technical article entitled "The influence of boron and carbon additions on the microstructure of sintered alpha silicon carbide" by W. Bocker and H. Hausner, taken from the American journal "Powder Metallurgy International" volume 10, No. 2, 1978, pages 87 to 89. The starting material used in this method is an alpha type silicon carbide powder. The material, to which gasoline is added first, undergoes treatment in hydrofluoric acid and is then washed several times to remove the silica and the residual oxygen from the powder. The powder thus obtained is ground in a ball-mill and then treated in hydrochloric acid to remove the iron left by the grinding. The powder is then heated to 700.degree. C. to remove the residual free carbon, and is then treated a second time in hydrofluoric acid. After further heat treatment at 1200.degree. C. under an argon atmosphere, amorphous boron and a carbon source are successively added to the powder, said carbon source being polyphenylene dissolved in benzene. After removal of the benzene in an air stream, a sample is taken by pressing powder impregnated with oleic acid in a steel die to a pressure of 100 N/mm.sup.2. Lastly, the sample is sintered under an argon atmosphere at a temperature of about 2000.degree. C.
The method described hereinabove has the disadvantage of being complicated. Indeed, it includes two chemical treatments in hydrofluoric acid which last for a long time. Further, these chemical treatments to not make it possible to remove completely the residual oxygen from the powder; this reduces the density of the ceramic obtained.
The present invention aims to mitigate these drawbacks and to bring into effect a simpler and more effective method for manufacturing a dense silicon carbide ceramic.